The long-term objective of this work is to determine the functional role of NEK2 in promoting cancer progression and to use this knowledge to develop novel therapies. The variability in survival of multiple myeloma patients ranges from only a few months to >10 years. We have previously shown that NEK2- expression is increased in multiple cancers including myeloma; higher levels of NEK2-expression induce cell rapid growth and resistance to multiple chemotherapeutics. This project builds upon our finding that when a specific gene (NEK2) that regulates the cell cycle is overexpressed, patients experience a clinically aggressive form and rapid death of myeloma and other cancers. We have made several striking discoveries supporting the hypothesis that NEK2 over-expression disrupts the normal cycle of tumor cell proliferation, resulting in poor survival for myeloma patients. Our goal to test the hypothesis will be accomplished by execution of three specific aims using both in vitro and in vivo models. Aim1: To examine the role of NEK2 in the development and progression of myeloma. We propose to evaluate whether myeloma cells with high-NEK2 expression are characterized with drug resistance in a large cohort of patients with myeloma at different stages; we will also test the growth and drug-resistance of primary myeloma cells with NEK2 high- or NEK2 low-expression in vitro and in vivo; we will introduce NEK2 into normal fibroblast cells and murine cancer-derived myeloma cell line that have low endogenous NEK2 expression, we will then analyze the effects of this alteration on cell transformation, cellular growth, and response to chemotherapeutic agents. Aim 2: to determine NEK2-mediated signaling pathways in cancer cell proliferation and survival. To achieve this goal, we will determine whether some cell growth related signaling pathways are required for NEK2-mediated cell growth and drug resistance in multiple myeloma. We will examine key substrates that directly interact with the NEK2 protein. Furthermore, gene expression profiling (GEP) will be performed on myeloma samples in remission and at relapse who also have GEP at baseline to identify genes that are regulated by NEK2 at different myeloma stages. Aim 3: to develop novel treatments based on targeting NEK2 or its signaling pathways. Through the screen of kinase inhibitor libraries, we have identified two small molecules that can specifically inhibit NEK2 kinase activity, and induce dramatic cancer cell death in vitro. We will use these molecules as a tool to explore their efficacy in killing myeloma cells in vivo. Inhibitors targeting these signaling pathways will be used alone or in combination with the current used chemotherapeutic drugs to evaluate their antimyeloma activities in vitro and in vivo.